Process of removing tin from columbium alloys



Patented Feb. 11,1936

UNITED STATES PROCESS or REMOVING TIN mom coLU mM ALLOYS Ernest F. Doom, Niagara Falls, N. Y., assignor, by mesne assignments, to Union Carbide and Carbon'Corporation, a corporation of New York No Drawing. Application March 21,

Serial No. 716,651

3 Claims.

The present invention relates to a process of treating metallic alloys and more particularly to a process of treating alloys of. columbium forthe removal and" separation of tin.

Naturally occurring columbium ores such as columbite are frequently associated with stanv niferous minerals. If such tin-contaminated ores v are smelted for the production of alloys of co1u m-. bium with-iron, silicon, or other metals, a major portion of the tin content of the ore will ordinarily be recovered in the columbium alloy. For certain uses to which the-columbium alloys are put, notably as a means of. introducing columbium into steel,a high "tin content is often desirable. The removal of the associated tin from columbite prior to smelting is rarely feasible in a commercial manner, when known methods of ore dressing are resorted to, and where a fairly complete removal, of tin is desired. Special chemical treat ments of the ore have been used heretofore, but all of them are relatively expensive.

It is an object of my invention to provide a means of cheaplyand relatively completely re-' moving'tin from columbium alloys.

I have found that if silicon is incorporated in a tin-containing columbium alloy in an amount exceeding a silicon to columbium ratio of about 1 to 6.5, the tin content thereof may be leached out. by means of hydrochloric acid or a similar acid. It appears probable, from my investigations, that when the silicon content of the. alloy is less than this ratio the tin is combined with. the columbium as an acid-insoluble compound. when thesilicon content of the alloy exceeds this} ratio, the tin is in a free or at least in a soluble form. This silicon-columbium ratio roughly corresponds with the silicide CbiSi, and it may well be that the relative afllnity of'columbium for silicon. is greater than the affinity of columbium for tin, so that, when suflicient silicon is' present to form the silicide, the tin is left in a free'or soluble'form. It will be understood, however, that this is merely a theoretical explanation and that this invention does not depend upon the correct- 3 nessof this theory. The presence of other silicide-formingelements in the alloy may alter the minimum ratio of silicon to columbium necessary for the best extraction'of tin. In general I prefer to use somewhat more silicon in the alloy than the ratio shown, this being considered more conducive to an easy solution of the tin. 4

In carrying out my process, columbium alloys which may be produced by smelting stanniferous columbium oxide ores, by using any suitable reducing agent such as carbon, aluminum, or silicon, may be treated for the elimination of tin.

The required silicon content of the alloy may be obtained by the reduction of silica, simultaneously with the reduction of the columbite ores, either 10 of silica naturally occurring in the ore, or of silica which may be intentionally added to the ore. Alternatively; a silicon-columbium alloy may be obtained by directly alloying a columbium alloy with metallic silicon.

The alloy produced by any of the above described processes is then comminuted and treated with a leaching agent. A leaching agent which has been found to be particularly suitable for the purposes of this invention is hydrochloric acid. However, other acidic agents, and particuwill usually require several hours, depending on the amount of tin to beextracted, the temperature, the concentration of the acid, and the size of the alloy particles being treated. I have found that the tin'can be practically completely extracted when the alloy iscomminuted'sothatthe particles will pass a 20 mesh screen, openmg), the particles being treated with hydrochloric acid of about 11 Baum. The acid treatment will frequently dissolve small amounts of some of the alloy constituents other than tin,. such as iron, but -I have found that ifery little, if any, loss of columbium'occurs. The concentration of acid is not critical, as I have employed dilute and concentrated acid with practically equal success. In general, an excess of acid-of fair concentration is to be preferred, as it hastens solution of the tin.

In practicing my invention, three lots of ferrocolumbium-silicon alloy containing varying ratios 7 of silicon to columbium were comminuted to 20 mesh and treated for 36 hours with a solution with two parts of the diluted acid. The results Q,

of this treatment are indicated in the following bium ratio isnearly l to 6.5, a substantial amount table: of the tin is removed by the treatment. With Alloy No.1 I a silicon content below this ratio, as in Alloy No. 1, the tin is completely insoluble, whereas 5 I Bermmat. mm with a higher silicon content, as in Alloy No. 3, 5

went mm the tin is substantially all removed by the acid treatment.

The columbium alloy treated by my process for the elimination of tin may be used directly for adding columbium to other metals, such as steel, or if a lower silicon alloy is desired the silicon may be removed or lowered by any of the conventional refining processes prior to such use.

Alloy No.2 I What I claim is: 1. The process of removing tin from columbium 15 Before treat- Aitertreatalloys which comprises introducing silicon into said alloys in an amount at least equivalent to that required to provide a ratio of silicon to columbium satisfying the formula CbzSi, and treating said alloys with aqueous hydrochloric acid.

2. The process of reducing the proportion of tin in tin containing columbium alloys, which comprises introducing silicon into such alloy in Largely iron lto columbium ratio of about 1 to 6.5, comminuting Before treat- Altertm tthe silicon-containing alloy and leaching it with a solution of hydrochloric acid.

3. The process of reducing the proportion of 40.42% tin which is contained in an iron-columbium {2 alloy, which comprises introducing silicon into g3: said alloy in a'iatio of about 1 to 6.5, comminutl mg ing the alloy, and leaching it with aqueous hydrochloric acid.

' ERNEST F. DOOM. It will be noted that where the silicon-colum- CERTIFICATE OF CORRECTION.

Patent No. 2,050,' 357. I February 11, 1936.

ERNEST F. DOOM. a

It is hereby certified that errorappears in the printed specification of the above numbered patent requiring correction as follows: Page 1 first column, line 14,, 'for "desirable read undesirable; and that the said Letters Patent should be read with this correction 'therein that the same may conform to the record of the case in the Patent Office.

, Signed and sealed this 17th day March, A. D. 1936.

Leslie Frazer (Seal) 4 Acting Commissioner of" Patents 5 Alloy No. 3 an amount at least equivalent to a silicon to 25 CERTIFICATE or CORRECTION.

Patent No 2,050, 357.

ERNEST F. DOOM. A

It is hereby certified that error in the printed specifioation of the above numbered patent requiring correction as follows: Page 1, first column, line 14, 'for "desirable" read undesirable; and that the sai Letiers tion 'therein' that the same may conform Patent should be read with this correc to, the record of the case in the Patent Office/ Signed and sealed this 17th day March, A. D. 1936.

appears Leslie Frazer (Seal) Acting Commissioner of Patents February 11-, 1936. 

